Effects of formation water influx on the bonding strength between oil well cement and the formation

Abstract In this paper, the effects of formation water on the construction quality of the cement-formation interface under static and water disturbance conditions were studied. The critical flow velocity of formation water that affects the construction quality was revealed. A flow velocity prediction model was established to provide a reference for the wellbore shut-in range of surrounding injection wells during the cementing operation. The test results and mathematical analysis show that the construction quality of annulus cores cured by formation water display no adverse effect when compared to that of the distilled-water-cured samples under static conditions. A flow velocity of 12 mL/h is the critical flow velocity of formation-water-cured samples under water disturbance conditions. The failure of the cement-formation interface with water disturbance results from the Ca2+ loss of the cement matrix. The flow rate and the composition of formation water show a synergistic effect on the failure of the cement-formation interface. This study is essential to improving the construction quality of clastic rock formations, which contain abundant formation water.